A South L.A. woman died during the most recent of the incidents involving the LAPD, all caught on tape. Chief Charlie Beck says all three are being investigated.

Three violent altercations caught on tape involving Los Angeles Police Department officers have rekindled the long-running debate about LAPD use of force and are shaping up to be a significant test for Chief Charlie Beck.

All three incidents occurred during seemingly routine calls and inexplicably turned violent.

Several weeks ago, a cellphone video showed four police officers tackling a 20-year-old Venice skateboarder they said was resisting arrest. One officer hit him in the face.

This week, videotape emerged in which two LAPD officers in the San Fernando Valley were shown slamming a handcuffed woman to the ground before appearing to give one another fist bumps. The woman, a nurse who was pulled over for holding a cellphone while driving, suffered large bruises to her face and body.

But the most serious incident came to light late Thursday, when LAPD officials revealed that a woman had died during a confrontation in July outside her South Los Angeles home. Police said the woman had gone to a police station to drop off her children because she said she could not take care of them. Police returned to her house to arrest her on suspicion of child endangerment.

"Each incident is disturbing," said Police Commission member Richard E. Drooyan on Friday. "In each of these cases, we are talking about different places in the department with different races and genders involved."

Beck spent Thursday night moving through the city and talking to officers about the incidents.

"I was in the field last night and visited half a dozen police stations," he said. "I looked hundreds of police officers in the eye as I discussed their responsibilities. I have faith in them."

Beck said all three cases are under investigation but stressed he does not believe they point to a larger problem within the department.

"I am very concerned about several of these incidents. I am not concerned about the overall quality or character of the Los Angeles Police Department," he said. "There are 10,000 LAPD officers who do a phenomenal job in very difficult circumstances every day. We have literally over a million enforcement contacts a year. Some of them don't go that well, and there's a variety of reasons."

Accusations of excessive force — particularly those caught on tape — have been a major issue in the LAPD dating to the 1991 beating of Rodney King and including the 2007 May Day melee at MacArthur Park in which officers used force on protesters as well as on some journalists.

Drooyan said he wants the commission to look at the three new cases to determine whether there are any patterns or "cultural issues" within the department that need to be addressed.

"We've had a relatively calm period since I came on the commission 2 1/2 years ago, and I have seen nothing to suggest a cultural issue," he added.

Connie Rice, a longtime L.A. civil rights attorney and LAPD watchdog, said the key thing to watch now is how the department investigates the cases.

"For me it's never that the incidents happen, it's the response to the incident," Rice said. "It's endemic to policing that there are violent confrontations. For the LAPD, the old default was excessive use of force. The question is, how far are they are in their transformation away from excessive force being the norm? Do I see movement away from that? Yes, at the top they've definitively changed. Do we still have long way to go? Oh, yeah."

Rice said she has faith that Beck will take the incidents seriously. "There's a real investigation.... It would be the opposite 25 years ago. There would be no investigations — there would be exonerations."

The South L.A. probe focuses on the death of Alesia Thomas.

On July 22, Thomas left her children, ages 3 and 12, at the LAPD's Southeast station. LAPD Cmdr. Andy Smith said Thomas dropped the children off in front of the station and told them to go inside. LAPD Cmdr. Bob Green told The Times on Thursday that Thomas told police she was a drug addict and felt she could not care for them.

Officers later went to her home. After questioning her briefly, they attempted to arrest her on suspicion of child endangerment. Police and one witness told The Times that Thomas violently resisted arrest.

According to an LAPD account, one officer took her to the ground by sweeping her legs from beneath her. Two others handcuffed Thomas' hands behind her back and attempted to lead her to a patrol car while a supervising sergeant observed, according to the department's version, officials said.

Two more officers were summoned as Thomas continued to struggle. A "hobble restraint device" — an adjustable strap — was tightened around Thomas' ankles to give the officers more control and she was eventually placed in the back of the patrol car, the LAPD account said.